Electroretinographic assessment of retinal function at high altitude

Area of Science:

• Ophthalmology
• Altitude Physiology
• Retinal Electrophysiology

Background:

• Hypoxia is crucial in retinal disease pathophysiology.
• Effects of high-altitude hypoxia on retinal function remain largely unknown.
• The Tübingen High Altitude Ophthalmology (THAO) study investigates these effects.

Purpose of the Study:

• To assess retinal function during high-altitude hypoxia exposure.
• To utilize electroretinography (ERG) for evaluating retinal layers.
• To correlate ERG findings with physiological parameters and acute mountain sickness (AMS).

Main Methods:

• Performed electroretinography (ERG) on 14 subjects at low altitude (341 m) and high altitude (4,559 m).
• Employed an extended ERG protocol to assess various retinal layers' functional integrity.
• Correlated ERG measurements with oxygen saturation, heart rate, and AMS scores.

Main Results:

• Significant alterations in scotopic sensitivity function, a-wave and b-wave implicit times, and photopic negative responses (PhNR) at high altitude.
• Decreased a-wave slopes and i-waves observed.
• Strongest correlation found between PhNR and O2 saturation (r = 0.68); photopic b-wave implicit time correlated with AMS severity (r = 0.57).

Conclusions:

• High-altitude hypoxia alters retinal function across inner, outer, and ganglion cell layers.
• ERG parameters related to combined rod-cone responses are most affected.
• Phototransduction and visual processing, particularly under rod-cone interaction, are primarily impacted by high-altitude hypoxia.